Planing Mechanism Based On Multi-tooth Tools And Performance Study Of Bipolar Plates Of Miniature PEMFC

The manufacturing cost of miniature fuel cells especially bipolar plates is the main restriction of its commercialization. In addition, low specific power of mass and volume is also a great barrier. The previous research shows that bipolar plate accounts for80%of the total weight and40%of the total cost of the battery. So in order to extend the application of miniature fuel cells, the following solutions should be focused on more attention: manufacturing cost, reduce the mass and volume of bipolar plates and increase specific power. In this communication, the miniature channels of graphite bipolar plates are manufactured with multi-tooth tool. Then the cutting mechanism of miniature channels and performance of miniature fuel cells with miniature channels are both studied experimentally and numerically. The main works are summarized as follows:(1) Planing mechanism of the process of miniature channels with multi-tooth toolBy changing the parameters of multi-tooth tool (rake angle and clearance angle, tooth width and pitch and height, surface texture of rake face and so on) and cutting parameters (cutting velocity, cutting depth, feed rate), their effect on bottom topography of miniature channel as well as edge broken and the size and shape of chips are studied. It is found that rake face and cutting depth including surface texture of rake face have great influence on the process quality of miniature channels. The results also show that if the cutting depth is large, negative rake angle with transverse grinding marks can inhabit edge broken but lead to more rugged residual graphite layer while positive rake angle improve the roughness of channel bottom. According to this, the method named double stroke process (DSP) is put forward: when feeding, cut the miniature channels with negative rake angle; when retracting, don’t lift the tool and mend the bottom with positive rake angle.(2) Test system and performance evaluationConsidering the operating conditions, the test system for single miniature fuel cells is set up, which include six main units:gas supply unit, humidification unit, pressure control unit, temperature control unit, load unit, data acquisition and processing unit. Then, the structure of single proton exchange membrane fuel cell and flow field are designed for the experimental comparison about electric performance. In addition, the system of performance evaluation is developed.(3) Research on fuel cell with miniature channelsIt is found that the specific power of fuel cells with miniature channels can reach two times of fuel cells with ordinary channels if the temperature of battery and pressure of reacting gas keep low. The possible reason is that the ridges of ordinary channels are wider which weaken gas reaction because gas has to cover a longer distance before reaching the ridges. As a result, the electric performance deteriorates. However, with the same conditions, miniature channels are more advantageous to uniform diffusion and distribution of gas. It can be concluded that the bipolar plates with miniature channels are suitable for the applications of small power and size of fuel cells.